1. Field of the Invention
This invention relates to dishwashers and in particular to means for separating soil from the dishwashing liquid in an automatic dishwashing appliance.
2. Description of the Prior Art
In one conventional form of automatic dishwashing appliance, dishwashing liquid is circulated through a dishwashing space by means of a circulation pump. The dishwashing liquid is collected in a sump portion of the receptacle defining the dishwashing space and is delivered to the pump through a suction passage. The pump discharges the dishwashing liquid through a delivery passage, such as to a rotary spray arm for spraying the dishes in the dishwashing space, or to other conventional means for delivering the dishwashing liquid in washing association with the dishes.
During the course of the dishwashing operation, soil, such as particulate food material, is picked up by the dishwashing liquid. It is desirable to separate the soil from the liquid so as to minimize the subsequent rinsing operations necessary to complete thorough cleaning of the dishes. A number of different devices have been developed for effecting such soil separation.
Illustratively, in U.S. Pat. No. 1,971,588 of Edgar S. Stoddard et al, a dishwashing machine is shown wherein the dishwashing liquid is delivered to a sump adjacent a rotary impeller. The impeller and sump are cooperatively arranged so as to cause the particulate material to move outwardly towards the circumferential wall portion of the sump and then downwardly along a bottom wall portion thereof into a collecting chamber. The impeller acts on the liquid inwardly of the circumferential wall of the sump so as to throw the dishwashing liquid, which has been thusly freed of a portion of the soil, back into the dishwashing space. The collected soil may be discharged through a drain duct by suitable valve control means.
Forrest A. Walker shows, in U.S. Pat. No. 2,657,695, a dishwashing apparatus provided with a centrifugal separation pump wherein the soil is carried down into a vat by the downflow of the dishwashing liquid to be forced outwardly by the centrifugal action of the impeller toward an outside wall of the sump. A perforated barrier is provided inwardly of the sump space so as to intercept food particles tending to move to the impeller thereby holding the soil in the sump space between the perforated barrier and the outer sump wall.
In U.S. Pat. No. 2,700,973 of Joseph A. Pietsch, a dishwasher with a soil separation chamber is shown wherein the dishwashing liquid is caused to flow along an inclined wall into overlying relationship with a depending sump portion in which the soil tends to collect.
Helmut Muller, in U.S. Pat. No. 3,765,430, shows an automatic dish rinsing machine having a centrifugal force separator wherein the circulation pump includes a second outlet for delivering a portion of the dishwashing liquid to a centrifugal separator in parallel with the main return flow of the dishwashing liquid to the dishwashing space.